Acceleration switch



Oct. 25; 1949.

L. A. OBRIEN v ACCELERA'VIIOSWITCH I' 2 Sheets-Sheet 1 v Filed Nov. 7,v194e;

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L- A. O'BREN ACCELERATION SWITCH 2 SheetSJ-Sheet 2 File- Nov'. 74, 1946lnrucnfor- Laurence 'A E] 'Evian Patented Oct. 25, 1949 ACCELERATIONSWITCH Laurence A. OBrien, South Orange, N. J., as-

signor, by mesne assignments, to United States of America as representedby the Secretary of War Application November 7, 1946, Serial No. 708,388

3 Claims. (Cl. 1023-702) This invention relates to anacceleration-responsive safety arming device for delayed arming ofelectrically operated projectile fuzes, and more particularly, to acombination acceleration switch and powder train interrupter.

The principal object of my invention is toinsure the greatest possibledegree of safety against premature explosions in projectiles of theabove type. Another object of my invention is to provide arming meansfor a projectile of the above type, to render the projectile safeagainst rough handling and dropping, and which cannot explode during orimmediately after set-back due to normal firing, as can known fuzes ofthis type,

if the normal firing mechanism should be damaged or imperfect. Ifexplosion immediately after set-back occurs the projectile may not havetravelled a safe distance from its starting point, and may be dangerousto the operator of the weapon. Previously known switches would be in anarmed condition immediately after setback, and so could be easilyexploded at this point.

In launching a rocket it sometimes happens that shortly after itsinitial acceleration, which causes the rocket to leave its launcher, therocket propellant instead of continuing to burn at the correct rate,detonates in a low-order explosion, which imposes a second accelerationimpulse on the fuze. It is an object of my improved arming device toprevent this low-order propellant explosion from detonating the mainexplosive charge of the rocket. I accomplish these objects by providingmeans for initiating arming of the fuze only when it has been subjectedto a set-back force of the same order of magnitude and duration asoccurs during normal firing or launching of the projectile, and bycompletion of the arming a substantial time interval later thaninitiation thereof. Thus the two events must occur seriatim before thefuze is fully armed so that it can detonate the explosive charge of theprojectile.

Other objects will become apparent as the invention proceeds.

More specically, my invention comprises an inertia switch which islatched into circuit-closing position only after sustained set-back, anda rotary powder-train interrupter which is released for movement intoits armed position only after the said latching operation is completed.Both of these operations are retarded by the action of an escapementmechanism. The inertia switch is operated by set-back against the actionof a driving spring on its shaft, and is released from said shaft by themechanism which latches it in circuit-closing position. The shaft isthen driven by the spring to align the detonator in its armed position,and simultaneously to close a final switch to complete arming of thefuze.

In the drawings:

Figtue 1 is a longitudinal section View of a projectile embodying myinvention.

Figure 2 is a longitudinal section View on a plane passing through thelongitudinal axis of the projectile and at right angles to Figure 1.

Figure 3 is a schematic perspective view of the main shaft and theelements mounted thereon, prior to setback.

Figure 4 is a perspective of the rotor and inertia member similar toFigure 3, showing the elements at the end of normal setback, but priorto nal arming.

Figure 5 is a view similar to Figure 4, showing the elements at the endof the arming action.

Figure 6 is a detail view showing the manner in which the catch is keyedto the shaft.

Referring to the drawings, shaft I is supported for rotation in frame 2,2. Eccentric weight 3 is releasably latched to shaft I by latch 4provided with dog 5, the latch and dog being pivotally fastened toweight 3 by pivot pin 6, and being urged into latching relation withcatch 'I on shaft I by spring 8. Catch I is fixed to shaft I forrotation therewith. Spring 9 biases shaft I and weight 3 in a clockwisedirection (as viewed in Figures 2 and 3) against stop pin 4I, which actson Weight 3 to limit its clockwise motion.

Fixed to shaft I for rotation therewith are squib drum I0 and gear wheelI2. Squib drum I0 carries flush on its outer surface arcuate contacts IIand I2, from which conductors I4 lead to squib I6. Brushes I8 and 20bear against drum I0 and are initially out of contact with contacts IIand I2, as shown in Figure 3. When drum I0 is in its final position,shown in Figure 5, brushes I8 and 20 engage contacts II and I2respectively to complete the electrical arming of the squib, althoughdetonation will not normally occur at this time, as the squib energizingcircuit is normally completed by a fuze (generally indicated at 32)which may be any known type of electrical fuze.

Gear wheel I2, which is keyed to shaft l, drives an escapement 22through a reduction gear system generally indicated at 24. The purposeof the escapement device is to retard the rotation of the shaft I ineither direction to insure the lapse of a definite time interval betweenany of 3 the successive stages of operation of the device, as will bedescribed below.

The shaft l is mounted in a projectile having an electrical fuze 32, theaXis of the shaft being perpendicular to the direction of motion of theprojectile, as shown in Figure 1. When the projectile is fired orlaunched, the force of setback acting on eccentric weight 3 forces ittoward the rear of the projectile, thus rotating shaft I in acounterclockwise direction. This rotation is retarded by the action ofescapement 22. If the set-back force continues for a sufciently longtime, weight 3 will ultimately assume the 'posi-` tion shown in Figure4, wherein spring 26 engages dog 5 of latch 4. Upon cessation of'setback, spring 9 tends to return the shaft I and weight 3 to theoriginal position. Since dog 5 cannot follow the initial return movementof Weight 3, because it is restrained by spring 2G, the latch 4disengages from catch l. is thus restrained in the position shown inFigure 4, while shaft l returns clockwise to a position beyond itsinitial position, as shown in Figure 5, where it is held by a suitablestop, such as stop 34 engaging boss 35 on frame 2. This return rotationis retarded by escapement 22 to provide a definite time delay for thisphase of the arming operation.

Weight 3 is provided with a wedge 3S, and in the final position ofweight 3, this wedge is inserted between the spring leaves of twoswitches 3S and 4D to simultaneously close both of these switches, afterwhich they are maintained closed due to the action of spring 2G on latch4. This will initiate the arming of the fuze by condition- Aing theelectric circuits thereof for operation, and iS applicable to any knowntype of'electri'c fuze.

When shaft l has returned to its final arming position, drum l0 will bevin the position shown in Figure '5 with squib I6 properly aligned withbooster Il for detonation, and arcuate contacts Il and l2 in electricalengagement with brushes I8 and 20 respectively. In this position thefuze is fully armed for operation, and when it transmits a 'detonatingimpulse to the electric circuit, the projectile will be exploded.

It will thus be seen that I have provided an arming device whichaccomplishes the objects of the invention in a compact, simple unitwhich 1 can easily be made sufficiently rugged to withstand the setbackand other forces to which it is subjected.

In the following claims I use the term setback in the sense in which itis conventionally employed with reference to military projectiles, asdenoting a rearward force due to acceleration of the projectile in thedirection in which it is red or launched, acting upon free-moving partsin the projectile.

I claim:

1. Arming device for fuzed projectiles comprising a rotary shaft, aninertia element consisting of an eccentric weight latched to said shaftfor rotation therewith, first stop means, means biasing said shaft forrotation in one direction to bring said element to bear against saidstop means in a position such that setback acting on said weight willtend to rotate the shaft against said biasing means, delay means forretarding rotation of the shaft in either direction, a switch actuatedby said inertia element upon sustained setback to initiate arming ofsaid device, means for unlatching said Weight from said shaft upon saidsustained setback, thereby rendering said stop means ineiective, arotary powder train interrupter normally carried by said shaft inunarmed position, and second stop means for stopping said rotaryinterrupter in armed position against the force of said biasing means apredetermined time interval subsequent to cessation of said sustainedsetback.

2. An arming device for fuzed projectiles comprising a rotary shaft,means biasing said shaft for rotation in one direction, an escapementgeared to said shaft for retarding rotation thereof in either direction,an eccentric weight latched to said shaft and offset therefrom to urgesaid shaft in the other direction upon setback, first stop means forlimiting rotation of said eccentricY weight in said first direction,arming initiation means actuated by said Weight upon rotation thereof inthe other direction to a predetermined position, means for unlatchingsaid weight from said shaft upon rotation to said predetermined positionto release said shaft for rotation thereof by said biasing means, arotary interrupter normally carried by said shaft in an unarmedposition, second stop means for stopping said rotary interrupter inarmed position against the force of said biasing means, and circuitmeans actuated by nal movement of said rotary powder train interrupterin its final position to complete the arming operation 3. Arming devicefor fuzed projectiles comprising a rotary shaft, an inertia elementconsisting of an eccentric weight latched to said shaft for rotationtherewith, first stop means, means biasing said Ishaft for rotation inone direction to bring said element to bear against said stop means in aposition such that setback acting on said weight will tend to rotate theshaft against said biasing means, delay means for retarding rotation ofthe shaft, means actuated by said inertia element upon sustained setbackto initiate arming of said device, means for unlatching said weight fromsaid shaft upon said sustained setback, thereby rendering said stopmeans ineffective, a rotary powder train interrupter normally carried bysaid shaft in unarmed position, and second stop means for stopping saidrotary interrupter in armed position against the force of said biasingmeans a predetermined time interval subsequent to cessation of saidsustained setback.

LAURENCE A. OBRIEN.

REFERENCES vClI'lED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,726,325 Varand Aug. 27, 19292,149,470 Schenk Mar. 7, 1939 FOREIGN PATENTS Number Country Date257,335 Great Britain Aug. 27, 1926

